Walls and ceilings made from gypsum wallboard panels are conventionally constructed by attaching the wallboard panels to framing members or studs, and filling and coating the joints between the panels with a specially formulated paste composition called a joint compound. Joint compounds may be supplied as powdered compositions (to be mixed with water at the jobsite) or may be premixed with water at the factory to yield a ready mixed (or paste) joint compound. A paste joint compound (Taping grade) is placed within and over the joint formed by the abutting edges of the wallboard panels, and a paper reinforcing tape is embedded in the joint with the joint compound which is then permitted to dry. Alternately, the reinforcing tape may be of non-cellulose composition, but of a size and shape similar to strips of paper joint tape. Alternately, the reinforcing tape may be of a fiberglass weave requiring the use of chemically setting type joint compounds. When the joint compound is dry, a second joint compound (Topping or Finishing grade) is applied over the joint, and it too is permitted to dry. It is usually necessary for a third application of a joint compound and, after the third coat is dry, it may be lightly sanded and may be conventionally finished with a decorative material (paint, texture or wallpaper) then applied to the wall. All three coats of joint compound may alternately be done with an All Purpose grade of joint compound. Ready mixed joint compound is typically supplied to the customer in either cardboard cartons or plastic pails in units having volumes of 3.5 to 4.5 gallons (13.25-17.03 L). Joint compound is supplied at a viscosity typically higher than what is applied at the jobsite. This allows the contractor to mix in additional water using a power drill and mixing paddle to achieve the desired application viscosity.
Ready Mix joint compound production is typically accomplished by blending the wet and dry ingredients in a mixer until smooth, adjusting the viscosity to a desired level through water addition, then filling and sealing containers to be shipped to customers. This process can be disrupted by use of ingredients which thicken very rapidly and take longer periods of time to fully wet out and drop in viscosity, leaving the combined wet and dry ingredients in the mixer competing for water through the typical mixing cycle and at a higher than desired viscosity. The above process results in mechanical limitations and problems such as binding of the wet mixer and overloading of the mixer motor. The higher than desired viscosity at the completion of the mixing cycle affects the ease of pumping and moving the material out of the mixing system and through the packaging line and also interferes with the lidding and closing of the container. Thus, there are mechanical limitations on the types of raw materials that can be used within a typical wet mixing system for manufacturing ready mix.
U.S. Pat. No. 6,476,099, incorporated by reference, discloses the addition of surfactant additives to joint compound to generate performance with reduced cracking, reduced shrinkage and reduction of surface finish defects after application to wallboard and other panel surfaces. The preferred surfactant additive was identified as sodium dodecylbenzene sulfonate (DDBSA). It has been found that a significant disadvantage and limitation for the use of DDBSA is that the joint compound will develop an extremely frothy and spongy appearance after the joint compound is packaged. The degraded appearance of the DDBSA modified ready mix joint compound can limit product acceptance by applicators upon opening the packaging, however product performance is excellent following remixing, which temporarily redisperses and reduces the size of the spongy, frothy air bubbles. Remixing is a standard practice by applicators to homogenize the joint compound and break down any gel or yield value, while adding water to reduce the viscosity of the joint compound to a point preferred for their current step in joint finishing process. Remixing and thinning is accomplished using a powerful drill and mixing paddle.